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BCI’s Subterranean Program team plunges into the deep to preserve and protect hidden species and their habitat

By Michelle Z. Donahue

Thanks in no small part to a certain nocturnal, crime-fighting hero, most of us are probably familiar with the concept of the bat cave. Comics aside, it’s largely true: roughly half of all bat species in the United States use subterranean habitats for some part of their life cycle—for mating, raising young, sleeping, hibernating, or as rest stops during migration.

Determining where this critical habitat is, and how best to protect it, is a primary mission of BCI’s Subterranean Program, or Sub-T. To say it’s hard work is the definition of an understatement.“I’ve been shot at, struck by a rattlesnake, stuck 180 feet down a shaft in a monsoon storm, nearly been trapped and burned by wildfire, waded through more feces than you can imagine, and been covered in fleas, ticks, leeches, and mites,” said Jason Corbett, Subterranean Program director. “That’s not a statement of bravado, just what parts of this job have entailed. And it’s just fine with me.”

Welcome to life underground.

Cave Evolution

BCI’s Sub-T Program was created in 2008 out of a series of cave and mine initiatives that have existed, in one form or another, since BCI’s beginnings in 1982. Throughout that time, BCI has been a part of a sustained effort by bat biologists across the country to ensure that closures of abandoned mines across the country took bats into account. Working with more than three dozen partners, including the federal Bureau of Land Management, state mining offices, other conservation and wildlife nonprofits, and private companies like Freeport-McMoRan, the Sub-T Program works to address a broad range of bat species and the threats they face.

Townsend's big-eared bats(Corynorhinus townsendii) are a common species encountered by the Sub-T team. Photo: Michael Durham / Minden Pictures.

Together with Shawn Thomas, Sub-T’s program manager, and Nathan Breece, who recently joined the team as its field lead, the team builds on the work that began several decades before. Though most of the Sub-T work takes place in the western U.S., the team has gone underground in locales as far-flung as Fiji, Peru and central Europe.

With an estimated 45,000 known caves in the lower 48 states, and 500,000 abandoned mines as counted by the U.S. Bureau of Land Management, it’s no small task. To date, the Sub-T program has surveyed over 5,000 mine features and 400 natural caves.

A number of projects are in process at any given time: White-nose Syndrome monitoring in Washington, Oregon, and Wyoming; surveys and bat gate installations in Wyoming; mine mapping and habitat characterization in Death Valley National Park in California; and working with the Department of Defense to implement the North American Bat Monitoring Protocol at White Sands Missile Range in New Mexico.

Many subterranean-reliant bats are sensitive to disturbance of their roosting sites, like the Townsend’s big-eared bat (Corynorhinus townsendii), which sometimes will up and move an entire colony within mere moments of sustained disturbance. Disruption takes many forms: unstable mining structure beginning to collapse, construction of a new neighborhood near a cave entrance, or people exploring mines out of sheer curiosity.

Climate change, too, takes its toll, shifting resources like water and food away from a roosting site.

“Maintaining a variety of underground spaces will be key to allowing bats to maintain a toenail hold, or being able to expand into different areas,” Corbett said. “In areas where bats might be stressed, they provide a space for bats to stay, and hopefully thrive.”

Abandoned Mine Initiative Like a classic Looney Tunes cartoon, some abandoned mine portals in the American West are rounded holes punched in a rocky cliff face. But others are not, yawning narrow and bottomless in the flat earth before your feet, obscured to its edges by scrubby mesquite and sagebrush.

Abandoned mines like these pepper the sprawling public lands of the United States. For humans and the surrounding environment, these sites can pose very real dangers, from falling down a shaft to runoff from mine tailings polluting water and soil.

But for many species of bats, they’re home. Many other birds, insects, small mammals, and even reptiles and amphibians also find these dark chasms to be perfectly comfy and cozy. At times, Thomas recalled, the team would go into a shaft, flick on their headlamps, and find a handful of wood rats staring back; recently, he advised a startled contractor with how to handle a Gila monster they’d found at the bottom of a 32-foot mine shaft. (The Arizona Game and Fish Department helped rescue it.)

Federal and state agencies are required to determine which of these mines should be “destructively closed,” or have their entrances demolished or their main shafts filled in. But before that happens, to rule out that the property provides habitat for wildlife, the Sub-T team comes in to help make those assessments. Most federal workers are prohibited by law from entering mines and other subterranean structures, so BCI’s staff fills in a critical gap.

Of the 5,000 mines that the Sub-T team has surveyed, each was being considered for destructive closure; the team recommended that more than 1,000 be kept intact as habitat, but closed off to human access by installing a bat-accessible gate.

The survey work itself is slow going; though the teams may visit anywhere between 20 to 50 BLM-selected sites in an average week in the field, many mines peter out before too long. Other sites require a deeper probe, careful navigation down drifts and shafts, avoiding vertical drops called “winzes,” meticulous data-keeping, and watching out for other animal use of the site.Sub-T has also been instrumental in helping the U.S. Fish and Wildlife Service recommend the lesser long-nosed bat (Leptonycteris yerbabuenae) for removal from the endangered species list. By surveying a large number of caves and mines in southern Arizona and New Mexico, identifying roosts, and reporting their findings to Fish and Wildlife, BCI’s efforts contributed to getting a solid sense of the stability of populations of lesser long-nosed bats in the United States.

“It’s not too hard to have a mine or cave on this Western landscape that’s unknown or hidden, and we wanted to make sure there wasn’t another roost of 10,000 bats out there,” Corbett said.

It’s critical to get down into these spaces to scope them out. One of the largest colonies of Mexican free-tailed bats, in the millions, was stumbled upon in an abandoned mine just five years ago by a private citizen. Some of these mines are so remote, it’s very possible a human hasn’t visited in a century. “We’re literally seen as the experts for making recommendations for how to protect these habitats,” Thomas said. “It can be a lot of effort, and feel like not much is happening. But something that looks like nothing from the surface can be a critically important place for bats.” ￼